Lycoming College                                                                                                                   Write name on back,

Chem 110, 2002                                          Exam III                                                                              upper right

1.   Matching:  match the items in the right column by writing in the letter of a selection from the items in the left. 

      A.  Pauli                                                                 _____  h                                                      

      B.   Bohr’s DE                                                         _____ 

      C.   Planck's constant                                               _____    -   

      D.  AX₅E                                                               _____  trigonal bipyramidal

      E.   Hund                                                                _____  6.626 x 10-34 

      F.   AX₅                                                                       _____  octahedral

      G.   speed of light                                                     _____  parallel spins when possible

      H.  DH_{rxn, estimated}                                                                 _____                                              sp³

      I.    AX₆                                                                  _____  no two e^- with the same four quantum numbers

      J.     =                                                                         _____                       2.998 x 108 m/sec

      K.  AX₄                                                                  _____  square pyramidal

      L.   Planck’s quantization, E =                                  _____  - 2.179 x 10^-18 J  - 

2.   Deduce the ground-state electron configuration (core notations acceptable) for:

      a)   zinc, ₃₀Zn

      b)   zinc(II) ion ion, ₃₀Zn²⁺

      c)   americium, ₉₅Am

      d)   Provide an electron occupancy (orbital box) diagram for the valence shell electron configuration of phosphorus, ₁₅P.

3.   a)   Calculate the energy (in joules), the frequency (in sec^-1), and the wavelength (in nm) of the light associated with the transition of the electron in a hydrogen atom from state n = 2 to state n = 3.

      b)   For the transition from state n = 2 to state n = 3, is the light absorbed or emitted by the atom? ______

4.   Name or give the symbol for the element that fits each description:

      ______a)  [Rn] 7s2

      ______b) Alkali metal with a 5s valence electron configuration

      ______c)  Of Na, Mg, Al, Si, the element whose big “jump” in successive ionization energies would occur between IE₂ and IE₃

      ______d) 1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰4p⁶ 5s¹4d⁵

      ______e) Heaviest element which has a half-filled p subshell

      ______f)  Element with the smallest first ionization energy

      ______g) Element with the smallest electronegativity (noble gases excepted)

      ______h) A fourth-row, d-block element having only two unpaired electrons (4^th row starts with K)

      ______i)  Another fourth-period, d-block element having only two unpaired electrons

      ______j)   Of  S, Cl, and Br, the element of smallest atomic radius

      ______k) Of S^2-, Cl^1-, Ca²⁺, the atom or ion having the largest radius

      ______l)   Of Ca, Cr, and Zn, the metal which would be paramagnetic

      ______m) An element whose “last-filled-in” electron has quantum numbers n = 3, l = 2, m_l = 2

      ______n) A non-metal incapable of octet expansion.

5.       In each of the following bonds, on which atom would a partial negative charge (d-), if any, be located:

a)    N^____C                                                 b)   C^____S                      c)   S^____F

Electronegativies are:    c_C  =  2.5          c_N  =  3.0         c_S  =  2.5         c_F  =  4.0        

Which of the bonds will be the most polar? ________    Which of the bonds is essentially nonpolar? _______

6.   The carbon-oxygen bond lengths in the series of molecules  H3COH,  H2CO ,  and CO are 143 pm, 123 pm, and 113 pm, respectively.  Draw complete Lewis structures for each of these molecules, and then explain the observed variation in bond length.  The formulas are written so as to indicate topologies.

      H3COH                                                      H2CO                                                  CO

7.   Use each of the following Lewis dot structures (correct for dots, but not necessarily for geometries) to predict the molecular shape, estimate the bond angle, indicate whether the species will be polar or nonpolar, and give the valence bond theory hybridization state which would best explain the central atom.

      a)                                       molec. shape __________; bond angle ______; polarity________; hybridization ___                                                                                                                              

      b}                                       molec. shape __________; bond angle ______; polarity________; hybridization _____

      c)                                       molec. shape __________; bond angle ______; polarity________; hybridization _____

      d)                                       molec. shape __________; bond angle ______; polarity________; hybridization _____

           
8.   A satisfactory Lewis structure for carbonate ion (CO3^2-)  looks like

      a)   Write in formal charges for each atom in the structure shown above.

      b)   What is the shape of this ion?  ____________________________

      c)   What is the O-C-O bond angle, in degrees? __________________________

      d)   How many sigma () bonds, total, are represented in the structure? _____;    pi () bonds? ________

      d)   Experiments indicate that all three carbon to oxygen distances in CO3^2- are equal, and intermediate between a single and double bond length.  Explain this observation, using dot structures as appropriate.

9.   Estimate DH_rxn for the bromination of acetone reaction, using information from the bond energy table shown below.

      Dot figures may help

      Bond          Energy, kJ/mol        CH₃COCH₃    +    Br₂    à    CH₃COCH₂Br    +    HBr     DH = ??

      H-H                 436

      H-Br                368

      C-C                  347

      C-H                  414

      C-Br                 276

      C-O                  360                                                                      

      C=O                 736

      Br-Br               193

10.  Consider the following compounds:

      CH₃CH=CHCl              CH₂=CHCH₃          CHF=CHCl               CH₃CH=CHCH₃              CH₃C   CCH₃

      How many of these five compounds can exist as cis-trans isomers?   0,    1,    2,    3,    4,  all 5

      For one of the compounds that you think can exist in cis and trans forms, draw and label better structural diagrams of each isomer below.  Also, with arrows pointing to each carbon, indicate the hybridization state of each carbon atom in your structures.